Process for producing magnesia



April 15, 1952 c. N. KIMBERLIN, JR

PROCESS FOR PRODUCING MAGNESIA Filed March 15, 1949 r nuwln ,W NM oh u Aix Us NQ #W m M WM M -I E V) b 0 E E Patented Apr. l5, 1952 UNITED STATES PATENT QFFICEv PROCESS FOR PRODUCING MAGNESIA Application March 15, 1949, Serial No. 81,594

Claims.

This invention relates to a process for the preparation of catalytic and adsorbent materials and more particularly to a process for the preparation of magnesia and magnesia containing catalysts and adsorbent materials.

The use of magnesia and magnesia containing materials is well known. These substances may be made by mixing powdered magnesium oxide, which has been prepared by calcining magnesium carbonate, with other materials such as silica, alumina, silica-alumina and the like.

It is the object of this invention to provide a new process for the preparation of magnesia and/or magnesio. containing catalysts and adsorbent materials by the hydrolysis of an alcoholate of magnesium and recovering the alcoholior reuse by decanting a separated liquid phase.

Factors which contribute to the commercial practicability of this invention include:

(l) The low cost of magnesium metal as a source of magnesia;

(2) The eliminati-on of all necessity for Washlng;

(3) The simplicity of the processing steps involved in the manufacture; and

(4) The use of a substantially water insoluble alcohol to insure substantially complete alcohol recovery.

The material prepared in accordance with this method is characterized by high purity and high surface area.

Magnesium metal reacts readily only with the lower, water soluble alcohols such as methyl or ethyl alcohol. If the alcoholate of magnesium formed with these alcohols is hydrolyzed, the reformed or regenerated alcohols are very difficult to separate and dry for reuse. This difficulty is avoided in the present process by treating the magnesium alcoholate derived from a water soluble alcohol with a substantially water insoluble alcohol which may contain a hydrocarbon diluent. The water soluble alcohol radical is displaced from the magnesium alcoholate and the Water insoluble alcohol radical is substituted for it. The water soluble alcohol thus reformed is distilled out of the mixture and is recovered dry and ready for reuse. The remaining magnesium alcoholate is then hydrolyzed with an excess of water or other aqueous medium forming hydrous magnesia and regenerating the water insoluble alcohol. The hydrous magnesio. forms a slurry with the excess of water from the hydrolyzing medium. The alcohol which is reformed or re generated by the hydrolysis step, together with 2 any hydrocarbon diluent separates readily from the slurry of water and hydrous magnesia and is easily removed and recovered by a simple process of decanting or the like. The slurry of hydrous magnesia is removed for further treatment.

According to this invention, the alcohol used for the formation of the magnesium alcoholate is any of the aliphatic alcohols of the general formula CnH2n+1OH where "11. is 2 or less but alcohols Where n is l is preferred. The alcohol chosen must be essentially anhydr-ous and-the commercial anhydrous methyl alcohol is satisfactory.

For the replacing alcohol, that is, the water insoluble alcohol whichis used to replace the water soluble alcohol radical from the magnesium alcloholate, an aliphatic alcohol of the general formula CnHznJfiOH where "n is 4 or greater may be used but the alcohols where "n is 5 or greater are preferred. The Cs and higher alcohols are less soluble in Water than the C4 alcohols and are therefore preferred in this process. The C4 alcohols have a solubility :in water under standard conditions of 9 or more grams per 100 cc. of Water Whereas the C5 and higher alcohols (except tertiary amyl alcohol) havea solubility in water under standard conditions of about 5.3 or less grams per cc. of water. For this invention, the maximum allowable solubility of the alcohol in water under standard conditions is about l5 grains of alcohol per 100 cc. of water but the preferred maximum solubility of the al-v ooh-ol in water under standard conditions is about 5.3 grams or less of alcohol per 100 cc. of water.

The alcohols which may be used as replacing alcohols in this process include n-butyl alcohol, secondary butyl alcohol, isobutyl alcohol but While, as pointed out above, these alcohols are operable, they are much less satisfactory and the following higher molecular weight alcohols are preferred: pentanol-l, pentanol-2, 2 methyl butanol-4, 2 methyl butanol-3, pentanol-B, hexanol-l, hexanol-2, hexano1-3, the various methyl pentanols, the various dimethyl butanols, the various heptyl alcohols, thevarious octyl alcohols, etc. including those alcohols substantially insoluble in water and liquid at the temperature of operation of the process.

l Instead of using any one of the alcohols singly as a displacing alcohol, mixed alcohols such as mixed amyl alcohols may be used. Mixtures of alcohols of different molecular Weights may be used.

cohol being used up or lost in the process.

Inorder to further facilitate the separation of the alcohol from the water, and in the preferred form of this invention, a hydrocarbon, such as a petroleum distillate boiling within the range of 200 F. to 500 F. or higher and preferably in the'range of 300 F. to 400 F. is added to the alcohol. Although the addition of the hydro carbon is. not necessary to the process, the use of the hydrocarbon diluent is preferred and has the following advantages:

l. The hydrocarbon serves as a solvent for the solid magnesium alcoholate; and

2. The hydrocarbon diluent greatly aids in the separation and recovery of the alcohol from the hydrous magnesia slurry after hydrolysis.

The formation of the alcoholate of magnesium using methyl alcohol as the. reactant.V alcohol. takes place in accordance with the following equation:

EQUATION I 2CH3OHl{-Mg`- Mg(OCI-Ia) 2+H2;

Thehydrogerr is in the gaseous state andescapes from the reaction.

The replacement step using amyl alcohol as the-replacement alcohol proceeds as follows:

EQUATION II The-reformed or regenerated methyl alcohol is' removed from the reaction products by distillation.

Upon hydrolysis, the magnesium alcoholate undergoes: the following change:

the-.replacing:alcohol being' reformed and going into solution again .with thehydrocarbon diluent. The alcoholFhydrocarbon mixture contains a small. amountof residual water as entrained and dissolved: water and is' freed from this residual waterf by ay simple process of distillation forreuse inthel process. The overhead gases from the dry-ing;V still are condensed, the condensate allowed-to settle, and upon settling. separates into awater layer and an alcohol-hydrocarbon layer, thelatter being recycled. to vthe drying still. The dried. alcohol-hydrocarbon mixture is removed from the bottom ofthe drying still and is ready for further use in the replacement step.

In the drawing, thegure represents one form ofk an apparatus suitable for carrying out one embodiment of this invention.

Referring to the drawing, numeral 2 designates a Vstorage hopper for metallic magnesium. This magnesium metal may be in the form of magnesium chips, turningsY or the like. Alloys of magnesium can be used but they are undesirable because they react much more slowly than magnesium metal uncombined. The magnesium metal is charged into reaction vessel 4 by means of'screw conveyor 6. Reaction vessel l is adapted to contain the reactants, metallic magnesium and a lower Water soluble alcohol such as methyl or ethyl alcohol. The reaction vessel is equipped with an inlet pipe `8 for the addition of make up methyl or ethyl alcohol, some portion of the al- The amount of alcohol added through inlet pipe 8 varies with the conditions of the process but is usually between 0.5% and 1.5% of the circu lating methyl alcohol stream. The reaction vessel is also equipped with an exit line I0 for removing gaseous products, including hydrogen, from the reaction, the reaction occurring in accordance with Equation I. The hydrogen produced is equivalent in purity to that produced electrically. It may be cooled and passed through a separator which strips. from it any entrained liquid, the liquid being returned to reaction vessel 4 and the hydrogen ltered, compressed and stored by means ofv equipment not shown.

The reaction of the magnesium metal with the methyl alcohol in vessel 4 may be carried out in the presence of a promoter or catalyst, such as a small amount of mercurio chloride, aluminumA chloride, iodine or the like. Ordinarily, however, no promoter is needed for the reaction proceeds to completion readily without one. The temperature in reactiony vessel i will approximate the boiling point of the reactant alcohol used. When methanol is used, for example, the. temperature in reactionV vessel 4 Will. be apprnxi-` mately 150 F.

Temperature controlling means such as a cool-- ing coil, not shown, may be contained in reactor vessel 4 to control the rate ofV reaction andprevent boiling up of the reactant alcohol.

From reaction vessel f4 the products of the reaction comprising a solution of magnesiumV alcoholate in excess alcohol are passed through line l2 and into replacement still i6. In the replacement still lll, the magnesium alcoholate is treated with a substantially water insoluble alcohol. This treatment, which .consists of .thereplacement step, takes place in .accordance with Equation Il.

The water insoluble alcohol enters the. replace ment still lllthrough line IIB.. Line I6 carries the substantially water insoluble alcohol from azdry ing still, hereinafter to be described, to thezreplacement still. Iii. Line i5. isequipped with i8 forthe introduction of additional water insoluble alcohol to the circulatingjstream. This additional water insoluble. alcohol is added to make up operating losses which vary with efciency of op eration. This would be expected to be in the order of from 0.5% to:1.5% of theA circulatingr water insoluble alcohol stream under normally efcient operation.

Replacement still it at atmospheric pressure is heated to a temperature within the range of 230 to 280 F., depending upon the boiling point of the replacing alcohol. At these temperatures the lower water soluble alcohol is vaporized and is removed as vapor through line 22, condensed in condenser 2li, and returned to reactor vessel 4. The temperature at the top of replacement still I4 will be about 150 to 160" F.

The substituted magnesium alcoholate collects at the bottom of replacement stil] i4 and is removed through line 2S to a hydrolysis zone 28. Water or other aqueous medium is simultaneously injected into hydrolysis zone 28 through line 30. In this hydrolysis Zone 26, which may be a two fluid nozzle, a centrifugal pump, or any other device for simultaneously contacting tWo fluids each with the other, the magnesium alcoholate is hydrolyzed forming hydrous magnesia and regenerating the substantially water insoluble alcohol in accordance with Equation III. The temperature in hydrolysis zone 23 is not critical but may be rating. vessel 34. Here the mixture may be alzwaar@ lowed to remain substantially quiescent for a period of about 1 to 10 hours but very slow stirring aids the separation. The mixture separates into two distinct layers, the upper alcohol and hydrocarbon layer as shown at 36 and the lower water layer containing hydrous magnesia in the form of a slurry as shown at 38. The vessel 34 and its contents should be maintained at a temperature or about 70 to 200 F. preferably 150 to 180 F. since settling seems to be somewhat better in this range. 'I'he water or aqueous solution added to the hydrolyzing zone 28 through line 30 should be in such'amounts so as to give about 3 to 5% slurry of hydrous magnesia in the aqueous layer. For example, for each 100 grams of magnesium metal used about 3 to 6 liters of water or aqueous solution should be used. This slurry is readily concentrated to as high as 10% solids content by continued settling.

The slurry of hydrous magnesia is Withdrawn from the bottom of settling tank 34 through line 40. It may be passed from line 40 through line 42 to another settling chamber, not shown, to concentrate the slurry further. Water is withdrawn off the top of the settled slurry and reused in the hydrolysis step to recover any suspended hydrous magnesia it may contain. The concentrated slurry may then be passed to a dryer presently to be described. The slurry without further concentration may also be passed from line 40 into line 44. If it is desired, the slurry in line 44 may be impregnated or mixed with another catalytic component by introducing a solution of such catalytic component through line 46 to line 44 leading to dryer 48. The impregnated slurry may then be'dried in dryer 48.

However, if a magnesia gel is desired, the slurry either with or without further concentration may be passed v.directly into dryer 48. The drying temperature in drying chamber 48 may vary between 220 and 500 F. depending upon the catalytic material treated and the results desired. After being dried the magnesia gel may be removed from the dryer 48 by means of line 49. l

It it is desired, the dried magnesia may be impregnated with another catalytic material in vessel 50. In this case, the dried magnesia is transferred from dryer 48 to vessel 50 by a screw conveyor or other means identified by reference character 52. A solution of the desired catalytic component may be introduced into vessel 50 through line 54. After a suiilcient contacting period, the impregnated catalytic material and excess impregnating solution may be Withdrawn through line 56 for further treatment in equipment not shown.

The alcohol-hydrocarbon mixture in layer 36 of settling tank 34 is withdrawn through line 58 by means of pump 60 to a drying still 62 where any dissolved or entrained water is removed by a simple distillation. Heat for the distillation is furnished by coil 64 but any other method of supplying heat to raise the distillation apparatus to the desired temperature may be used. For a 50-50% volume mixture of amyl alcohol and a hydrocarbormpiluent boiling within a range of 300 to 400 F. this temperature will be about 250 F. to 280 F. The vaporized Water which carries with it some small portion of the hydrocarbon-alcohol mixture passes from the top of drying still 62 through line 66 and then through condensing coi] 68 into separator 10. Gravity separation takes place in separator 10 forming a bottom water layer 12 and a top alcohol layer 14. The Water is withdrawn from separator 10 through line 16 and is passed to line 30 for reuse in the hydrolysis step. Any alcohol and/or hydrocarbon dissolved in the water is returned to the system with the Water.

The alcohol-hydrocarbon layer in separator 10 passes through line 18 and into line 58 Where it is reintroduced into drying still 62.

The alcohol-hydrocarbon mixture that has been substantially completely freed of any dissolved or entrained water by drying still 62 is passed through line I6 and into replacement still I4. The temperature of the mixture in line I8 will be at the boilingtemperature of the mixture being used. v

The invention is Vfurther described and illustrated by the following examples.

Example 1 384 g. magnesium turnings were dissolved in 8v liters of anhydrous methyl alcohol. Cooling by an internal coil was necessary during the course of most of the reaction. To the solution of magnesium methylate was added 8 liters of amyl alcohol and 8 liters of Varsol (a hydrocarbon boiling between 300-400 F.). The methyl alcohol was then distilled off. The solution of magnesium amylate in excess amyl alcohol and Varsol was hydrolyzed by mixing with 16 liters of water. The layer oi? Varsol and regenerated amyl alcohol Was decanted and dried for further use by distilling out the small amount of dissolved and suspended water. The slurry of hydrous magnesia was dried in an oven heated at 250 F. The product was a magnesia gel having a surface area of approximately 500 square meters per gram. It is useful as an adsorbent or as a catalyst base.

Example 2 384 g. of magnesium turnings were dissolved in 8 liters of anhydrous methyl alcohol, cooling by an internal coil was necessary during the course of most of the reaction. To the solution of magnesium methylate was added 8 liters oi' amyl alcohol and 8 liters of a hydrocarbon diluent boiling between 300 to 400 F. From this mixture methyl alcohol was distilled ofi. The solution of magnesium alcoholate in excess amyl alcohol and hydrocarbon diluent was hydrolyzed by mixing with 16 liters of water. The layer of hydracorbon diluent in regenerated amyl alcohol was decanted and dried for further use by distilling out the small amount of dissolved and suspended Water.

To the magnesium slurry was added 86.6 g. of ammonium molybdate (82% molybdenum oxide) which was dissolved in one liter of water. The mxture was dried in an oven, heated to 250 F. and activated by heating to 850 F. 'I'his catalyst comprised approximately magnesium oxide and 10% molybdenum oxide and is useful for the treatment or hydroforming of naphtha in the presence of hydrogen for improving the octane number of the naphtha.

Example 3 The magnesia slurry was prepared exactly as in Example 2. To this was added a solution of 118 g. of ammonium dichromate in one liter of Water. The mixture was dried in an oven at 250 F., and activated by heating "at 850 F. This catalyst comprised approximately 90% magnesium oxide and 10% chromium oxide. It is useful for improving the octane number of naphtha.

Although it is not necessary to use a promoter to catalyze the freaction between magnesiametal and thefwater solublealcohol, it'may be-advanf tageous under certain conditionsr to use av promoter such as small amounts of mercury, mercurio chloride,V and the like. Ordinarily, the amount of mercury will be within a range of from 6.05 to 0.5 weight per cent based onthemagnesium metal. When only a small amount of magnesiav is to be made, it may not be worth while to recover this mercury. However, when large quantities of magnesaare to be. made, thetotal amount of mercury; used becomes considerable; Also thereV is a safety hazard from mercury vapors arising from the drying and calcining ofthe-magnesia catalyst where the :mercury is not first separated.

This mercury is easily recovered by contacting the solution of magnesium containing the mercury :which is in the form of a colloidal dispersion with -a metal vsuch as copper or silver which readily formsV an amalgam with mercury but which is non-reactive with alcohol. p

This contacting is done prior to the hydrolysis step. The .metal may be supported on a carrier suchas pumice, silica gel, alumina or other po- Vrous materialsA so that a high surface area will be presented. The metal readily absorbs the suspended mercury leaving the alcoholate solution Virtually free of mercury.

After the metal has absorbed the mercury to a point where its efi'iciency for further absorpt-ionvis-reduced the mercury is recovered from the amalgam by heating thus leaving the metal in a condition suitable for reuse.

The recovered mercury may likewisebe reused fortheyreaction of `magnesium with alcohol. The temperature at which it is necessary toheat the amalgam in order to distill oli the mercury will vary according to the metal that was employed and also according to the residual amount-of mercury which it is considered permissible to leave. associated with the metal for reuse. In general, it will not be necessary to completely free the metal of mercury before it is reused. Inany case a temperaturek higher than 1000 F. should not be necessary for this distillation.

Whatis claimed is:

l; A process for producing magnesia which comprises reacting a substantially anhydrous and water soluble lower aliphatic alcohol with magnesiumv metal to form magnesium alcoholate, treating the resultant magnesium alcoholate with a substantially water insoluble higher aliphatic alcohol, hydrolyzing the resultant substituted magnesium alcoholate with ari-aqueous medium to form a hydrous magnesia and a separate lay,- er comprising water insoluble alcohol, separating the regenerated water insoluble alcohol from said hydrous magnesia and recovering the hydrous magnesia so formed. Y

2;. A process for producing magnesia which comprises reacting a substantially anhydrous water soluble lower aliphatic alcohol with metallic magnesium to form magnesium alcoholate,

4. Aprocessaccording tol claim 2. in which. the substantially anhydrous water soluble lower ali phaticalcohol is methyl alcohol.

5. The process according to claim 2 in whichV the substantially water insoluble. alcohol is an alcohol containing 4 or more carbon atoms. and has a Asolubility in water of less than. about 15 grams per cc. under standard conditions.

6. The process for producing magnesia which comprises reacting metallic magnesiumwith a substantially anhydrous water soluble lower aliphatic alcohol, treating the magnesium alcoholate so formed with a mixture comprising a substantiallyvr water insolubleA higher aliphatic alcohol and alpetroleum distillate, hydrolyzing, the .resultant substituted magnesium alcoholate-with an aqueous medium, allowing the regenerated alcoholfpetroleum distillate to separate from the hydrous magnesia in a settling zone, passinggthe regenerated alcohol-petroleum', distillate mixtureto a drying zone, drying of regenerated al cobol-petroleum distillate mixture, condensing the overhead fraction from the drying zone and passingitto a separation zone, allowing the-said condensate to separate into a water layer and a regenerated alcohol-petroleum distillate layer in said separation zone, returning the dried regenerated alcohol-petroleum distillate mixtureto the process and removing the hydrous magnesia from said settling Zone to a drying zone and drying the hydrous magnesia.

7. A process for producing magnesia containing substances whichcomprises reactingmetallic magnesium with a substantially anhydrous water soln uble lower aliphatic alcohol, treating the magnesium alcoholate so formedwith a substantially water insoluble higher aliphatic alcoholtoform a substitutedmagnesium alcoholate, hydrolyzing the substituted magnesium alcoholate to form `hydrous magnesia and water insoluble alccohol, allowing the water insoluble alcohol to separate from the hydrous magnesa as a separate-layer, drying the last mentioned layer, returningsaid treated alcohol to the process and recovering hy*- drous magnesia from the reaction.

8. A process for producing magnesia containing substances which comprisesreacting metallic magnesium with a substantially anhydrous water soluble lower aliphatic alcohol, treating the magnesium alcoholate so formed with a substantially water insoluble high aliphatic alcohol-to form a substituted magnesium alcoholate, hydrolyzing the substituted magnesium alcoholate to form hydrous magnesia and water insoluble alcohol, separating the water insoluble alcohol and recovering hydrous magnesia.

9. A process for producing magnesia which comprises reacting a substantially anhydrous water soluble lower aliphatic alcohol with metallic magnesium to magnesium alcoholate, treating the magnesium alcoholate so formed with avmixture of a substantially water insoluble higher ali'- phatio alcohol and petroleum distillate so that the water soluble alcohol is displaced from the magnesium alcoholatevby the water insolublealcohol, recovering the displaced wat@` soluble al'- cohol, hydrolyzing the substituted magnesium ale coholate so formed, separating the aqueous'phase from the regenerated alcohol-petroleum distillate mixture and recovering the hydrous magnesia.l

l0. The process for producing magnesia which comprises reacting metallic magnesium withv a substantially anhydrous water soluble lower aliphatic alcohol, treating the magnesium alcoholate so formed with-a mixture comprising .a substan:

9 tially Water insoluble higher aliphatic alcohol and a petroleum distillate under conditions such that the water soluble alcohol is displaced from the magnesium alcoholate and the Water insoluble alcohol is substituted therefor, recovering the displaced water soluble alcohol, hydrolyzing the re-` sultant substituted magnesium alcoholate with an aqueous medium, allowing the regenerated alcohol-petroleurn distillate to separate from the hydrous magnesia in a second zone, separating the regenerated alcohol-petroleum distillate and passing it to a drying zone, drying the regenerated alcohol-petroleum distillate, condensing the overi head fraction from the drying zone and passing it into a separation zone, allowing the said condensate to separate into a water layer and a regenerated alcohol-petroleum distillate layer in said separationzone, returning the dried. regenerated alcohol-petroleum distillate to the process settling zone toa drying zone and drying the hydrous magnesia.

CHARLES N. KIMBERLIN. Je.

10 i REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,069,404 Cunningham Feb. 2, 1937 2,234,267 Chesny Mar. 1l, 1941 2,287,083 Cohen June 23, 1942 2,491,033 Byrns et al Dec. 13, 1949 FOREIGN PATENTS Number Country Date 490,388 Great Britain s Aug. l5, 1938 OTHER REFERENCES Organic Chemistry by Whitmore, 4th edition.

D, Van Nostrand Co., Inc., New York (1937) and removing the hydrous magnesia from said 20 p 

1. A PROCESS FOR PRODUCING MAGNESIA WHICH COMPRISES REACTING A SUBSTANTIALLY ANHYDROUS AND WATER SOLUBLE LOWER ALIPHATIC ALCOHOL WITH MAGNESIUM METAL TO FORM MAGNESIUM ALCOHOLATE, TREATING THE RESULTANT MAGNESIUM ALCOHOLATE WITH A SUBSTANTIALLY WATER INSOLUBLE HIGHER ALIPHATIC ALCOHOL, HYDROLYZING THE RESULTANTS SUBSTITUTED MAGNESIUM ALCOHOLATE WITH AN AQUEOUS MEDIUM TO FORM A HYDROUS MAGNESIA AND A SEPARATE LAYER COMPRISING WATER INSOLUBLE ALCOHOL, SEPARATING THE REGENERATED WATER INSOLUBLE ALCOHOL FROM SAID HYDROUS MAGNESIA AND RECOVERING THE HYDROUS MAGNESIA SO FORMED. 